Objective    To study the effect of RNA-interfered survivin gene on chemosensitivity of breast cancer cell line SKBr-3 to doxorubicin．    Methods    A shRNA expression vector

ΔpcDNA3-H1-S1

was constructed according to the specificity of survivin gene. SKBr-3 cells were transfected with liposomeencapsulated plasmids and positive clones were screened with G418. SKBr-3 cells were divided into RNA interference group

liposome control group and blank control group. Change of morphology in cells transfected with 0.5 μg/ml doxorubicin was observed under an optical or electron microscope. Cell apoptosis was detected by TUNEL assay with Annexin-Ⅴ  fluorescence staining

and inhibiting rate of cell proliferation was detected by MTT assay.     Results    The survivin gene sequence specific shRNA expression vector resistant to neomycin was successfully constructed

which was confirmed by DNA sequencing. The morphologic change of apoptotic cells was observed in RNA interference group. The rate of apoptotic cells was significantly higher in RNA interference group than in liposome control group and blank control group [(23.6±4.8)% vs (4.1±1.1)% and (3.2±1.4)%] after TUNEL staining (P0.05)

indicating that the sensitivity of SKBr-3 cells to doxorubicin was increased in RNA-interfered vector. The rate of apoptotic cells was significantly lower in liposome control group and blank control group than in RNA interference group [(17.43±3.12)％ and (20.51±4.67)％ vs (68.76±8.49)％] after Annexin-V staining (P0.05).     Conclusion    The chemosensitivity of  SKBr-3 cells to doxorubicin can be significantly increased by inhibiting the expression of survivin gene with RNA interference technology．